So far as I know, there is no code that would require a means of egress through the kitchen. In addition, the adjoining bedroom is on the first floor with an outside wall and windows. Our codes are different for commercial and residential construction regarding egress from rooms.
As for any cost savings by doing that, with or without the door, the plumbing remains the same. Location is roughly in the middle of the house, and the floor beneath it is the basement. It is a log home, so running any utilities inside the outer log walls is quite difficult, but that is not a factor here. Inside walls are hollow as is typical in most construction. The wall surfaces are individual tongue and groove siding, which will make modification and repair a bit more complicated than if the walls were plaster or drywall.
I think it is just a poorly thought out design. I posted it, because it get a little laugh every time I think about what the designer's thoughts must have been.
John